Switched Reluctance Generators

This tutorial is on Switched reluctance generators (SRGs). The SRGs are double-saliency electric generators that have non- over-lapping stator multi-phase windings & containing passive rotors. They could also be assimilated with stepper motors with position-controlled pulsed currents. Multiphase configurations are necessary for smooth power delivery & eventual self-starting & for motoring process, if the application requires it. SRGs were studied mainly for the following:

·       variable speed operation as starter/generators on hybrid electric vehicles,

·       as power generators,  on aircraft and

·       For wind energy conversion.

They may also be useful for super-high-speed gas turbine generators that range from kilowatt to megawatt (MW) power per unit. The distinct features of SRG are highlighted in paragraph below.

“As SRGs do not have permanent magnets (PMs) or rotor windings, they are available at low cost, simple to manufacture, & can operate at high speeds and in high-temperature environments.”

In automobile applications, an SRG is required to execute over a wide speed range to meet the terms with the internal combustion engine (ICE) that drives it. In case of wind energy conversion, limited smaller speed range is required to extract additional wind energy at lower mechanical stress in the system. Aware of the very rich literature on SRMs, following are the representative aspects of SRGs study:

•      Practical topologies and principles of operation

•      Characteristics for performance evaluation

•      Design for wide constant power range

•      Converters for SRG motor (M)

•      Control of SRG as starter/generator with and without motion sensors

The presence of a handful of companies that fabricate & dispatch SRMs & vigorous recent proposals of SRGs as starters/alternators for automobiles & aircraft (ranging to 250 kW per unit) seem adequate reason to follow the SRG study on broader scale.